Tonle Sap Lake, Cambodia: Southeast Asia’s Ultimate Wetland Haven


Black-headed Ibis in flight Photo Stephan Lorenz

As soon as we entered the boundary of the reserve birdlife burgeoned, first in twos and threes, then small flocks to hundreds, and with each successive turn of the channel the water birds amassed as if our boat was slowly drifting back in time. The count of Spot-billed Pelicans, enormous fish gobblers, rose from singles to small gangs that churned the water as they took flight from our approach. The namesake fine speckling on the bill clearly visible, their pale-eyed look stuck between annoyance and surprise.


Spot-billed Pelicans are still very numerous in the Prek Toal Reserve Photo Stephan Lorenz

After an especially sharp corner in the stream, an enormous Greater Adjutant looked up from its reading of the waters and sagely pondered our presence with glaring eyes like a prehistoric beast. The bird decided to take flight, with its broad, black wings beating deeply in the cool morning air and its massive, naked head plus monster bill seemingly dragging it down. Even the largest fish in these waters must live in constant fear, given the size of the adjutant’s bill. I wondered how any fish survived these stabbing implements punching the water’s surface in a furious feeding frenzy.

The Greater Adjutant lumbered to a tree and landed next to a Lesser Adjutant, a closely related stork that alone would stand out by size, but next to its rarer and larger cousin, the appropriately named Lesser Adjutant looked actually small. I wanted to take another picture, but the boat drifted on, relentlessly deeper into a wildlife spectacle. Around the next bend stood a half-dozen Greater Adjutants, reaching nearly five feet, they towered over us as we sat in the boat. We were outnumbered and the birds, sizing up the situation, stood their ground as we passed. The next few hours passed among numbers of birds I have rarely seen anywhere else in the world, comparable to Argentina’s Iberia Marshes or perhaps the Pantanal in Brazil. Prek Toal is Southeast Asia’s last remaining stronghold for large water birds. I stared in amazement and thought that this is what it must have been like hundreds of years ago.


Greater Adjutant is one of the specialties at Prek Toal Reserve and is a very rare species in Southeast Asia Photo Stephan Lorenz

Cambodia’s Prek Toal Core Bird Reserve offers the final chance for several endangered birds in the country and larger region, including the Spot-billed Pelican, Milky Stork, Painted Stork, both adjutants, Black-headed Ibis, and Oriental Darter. It is also a haven for more widespread waterbirds, harbors great plant diversity, and many other aquatic animals, including the critically endangered Siamese crocodile. The reserve is located in the northwestern section of the Tonle Sap Lake, Southeast Asia’s largest freshwater lake. This seasonally inundated lake captures floodwaters from the mighty Mekong along the Tonle Sap River, which flows into the basin, filling the lake during the monsoon season, and streams in reverse during the dry season, returning the waters to the Mekong River.

The extent and flood levels of the lake vary dramatically with the changing seasons and birds have adapted to take advantage of the high concentrations of food, nesting in large rookeries when the channels narrow and fish become concentrated in receding marshes. People have also adjusted, migrating about the lake in literal floating villages, profiting on the density of fish. In addition to the fishermen and their families living on the lake, several million people depend on it for water, food, and transportation. The lake and the surrounding provinces have been decreed as the Tonle Sap Biosphere Reserve and the Prek Toal Core Bird Reserve was declared a RAMSAR site, officially establishing its status as a wetland of international importance.


Painted Storks (pictured) are common and the rarer Milky Stork can be found Photo Stephan Lorenz

We witnessed this importance firsthand as our narrow boat slowly motored along the twisting channel, deeper into the ancient swamp. The previous day we had crossed wide expanses of open water after we left the main dock at Chong Kneas. The boat stuttered across flat water, first along a murky channel busy with other vessels and then past scattered, floating houses. Birdlife was nearly absent on the open lake and we only glimpsed the occasional Whiskered Tern. By the time we arrived in the Prek Toal floating village is was already after dark.

The following day we woke up well before sunrise and after a quick breakfast in the floating village, motored in suffused dawn light towards the entrance of the reserve. Our narrow boat, captained by a local fisherman and with directions of an expert guide from the Sam Veasna Center we entered the reserve, unceremoniously crossing a weir of bamboo and sand, but immediately drifting into an aqueous landscape with a primordial heartbeat. Dense reed beds and thickets bordered the margins of the stream and higher ground supported stands of dipterocarp forest. A low fog hugged the winding stream, extending misty fingers along oxbows choked with floating vegetation.


Egrets, egrets everywhere like this Intermediate Egret Photo Stephan Lorenz

Widespread herons and egrets were incredibly numerous, with the short-necked Intermediate Egret being most common, but Great and Little egrets were also present to round out the trio of blanched waders. Colorful Purple Herons and the plainer Gray Herons stood vigil along the edge of the channel, occasionally jabbing with lighting-speed at invisible prey. The smaller Striated Herons and Chinese Pond-Herons hugged the well-vegetated sections and flushed in alarm as we passed. Catching a glimpse of the small bitterns that call the lake home required more serendipity than skill, since Yellow, Cinnamon, and even Black bitterns flushed at random from dense reed beds and if our eyes weren’t affixed to the right spot at the right moment, the birds were gone as soon as someone called them out.


A rare Milky Stork (right) next to its more common cousin the Painted Stork (left) Photo Stephan Lorenz

While the massive adjutants commanded most of our attention, there were various other stork species too. We watched a near constant procession of Asian Openbills flying overhead and in a few swampy corners we found flocks feeding among floating vegetation. These medium-sized, black and white storks have an odd bill that appears permanently stuck in mid-sentence with the lower mandible bent to leave a gap. This bill shape apparently aids in cracking snail shells, the preferred food of the species. While the majority of storks stuck to the traditional black and white dress, the Painted Stork wore splashes of rose-colored feathers and a crimson head with yellow bill. We watched several flush from the shallow water and jostle for perches in the scattered trees. Sharp eyes picked out a stork that looked like a washed out version of the former, but this was not a faded individual, but the much rarer Milky Stork that still occurs within the reserve.


Gray-headed Fish Eagles are numerous Photo Stephan Lorenz

Three species of cormorants, Indian, Great, and Little rounded out the larger piscivores, and mobs of them dove for fish in the deeper sections of the channel. The snake-like heads and necks of Oriental Darters popped up every hundred feet and White-throated, Black-capped, and Common Kingfisher finished off the smaller fish, diving head first from low branches overhanging the water.  


Oriental Darter Photo Stephan Lorenz

It was not all about gangly legs and lengthy bills since a variety of raptors and songbirds thrive in the protected area, most notably the Gray-headed Fish-Eagle. We spotted a handful of these powerful raptors scrutinizing the water from tall perches, their formidable talons flexed to strike any fish that miraculously survived the labyrinth of gulping pouches and dagger-like bills downstream. Our knowledgeable guide was eager to show us nesting Buffy Fish-Owls, which are very rare in Cambodia and we watched two birds stare back at us indifferently. When the channel narrowed to a cul-de-sac we checked some trees and added a nice mix of passerines, including Malaysian Pied Fantail, Dark-necked Tailorbird, Pin-striped Tit-Babbler, and Plain-throated Sunbird.


Buffy Fish-Owl was only recently discovered at the Prek Toal Reserve Photo Stephan Lorenz

The Sam Veasna Center organizes birding trips to the preserve and this non-profit organization not only does an excellent job showing visiting birders Cambodia’s avifauna, but can also be credited with saving and protecting populations of  some of the most endangered birds in the world. Percentages of the proceeds from tours flow back into communities and help safeguard threatened birds. It is best to visit the Prek Toal Reserve during the dry season, when narrowing waterways concentrate fish and predators, making the water birds easier to find. The ideal time to bird in Prek Toal is from December to April.

It is possible to spend the night in the Prek Toal floating village, but accommodations will invariably be basic in every sense of the word. We stayed on terra firma, at least during the dry season, in the government environmental center, a large, concrete rectangle set on twenty foot tall pylons on the edge of the village. The rooms came with free rodents and suspicious holes in the ceiling. There was running water in the bathrooms, although most of it just flowed across the floor. In other words, if visitors like a bit more creature comforts it is advisable to stay in Siem Riep, Cambodia’s tourism capital due to Angkor Wat, which offers a wide variety of accommodations. The advantage of staying in the floating village of Prek Toal is that it enables birders to enter the reserve at the crack of dawn. This allowed us to serenely float past hundreds of birds that had not been disturbed by other visitors yet. Meals are available at a community restaurant in the village and it would be a good idea to purchase some of the local handicrafts to support the community.

Prek Toal Preserve may represents Southeast Asia’s “ultimate” water bird paradise for its significant populations of endangered storks, pelicans, and herons, but it is also the “ultimate” chance to rescue something that has been lost in other parts of the region. We have an obligation to preserve these places. Areas that allow glimpses of the past and reminders of what has already been lost.


Lesser (left) and Greater Adjutants perched together, revealing the noticeable size difference Photo Stephan Lorenz



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